Skin renewal can be stimulated by removal of the outer keratinous layer of the skin system. Such removal can be effected mechanically, for example, by rubbing with an abrasive composition, or chemically. Chemical exfoliation and peeling are effected by agents that interact with the complex structure of the skin, removing the outer layer to expose the underlying layers. Skin-renewal stimulating compositions and agents can provide anti-aging benefits, for example, a reduction of keratoses, freckles, wrinkles, fine lines and epidermal and dermal atrophy. The newly exposed skin is smoother and appears younger.
In recent years the use of cosmetic and pharmacological formulations containing skin-renewal simulating acids, such as alpha hydroxy acids (“AHAs”) or retinoic acid, to obtain antiaging and dermatologically therapeutic benefits has become widespread. Scientific and clinical reports, as well as much subjective evidence, have shown that substantial improvements in skin appearance and condition can be obtained by means of skin-renewal stimulating acids, which are believed to be attributable to increased rates of skin cell renewal, and the removal of outer layers of dead cells. But it is also well known that skin-renewal stimulating acids can be irritating, and that the irritation they induce is often a long-term effect manifested several weeks after use of the acids. In extreme cases the irritation can be severe and painful.
Skin renewal stimulating acids are also effective for treating acne, a common inflammatory pilosebaceous disease characterized by comedones, papules, pustules, and superficial pus-filled cysts. The earliest symptom of acne is hyperkeratosis of the upper part of the pilosebaceous follicle, which leads to obstruction of the pilosebaceous follicle with consequent formation of the comedone composed of sebum, keratin and microorganisms, particularly Propionibacterium (Corynebacterium) acnes. Lipases from P. acnes break down triglycerides in the sebum to form free fatty acids, which irritate the follicular wall. Retention of sebaceous secretions and dilation of the follicle may lead to cyst formation. Rupture of the follicle with release of the contents into the tissues induces an inflammatory reaction that may heal with scarring.
Salicylic acid is a well recognized anti-acne ingredient that causes a reduction in intercellular cohesion of the corneocytes. It is believed that salicylic acid also works by dissolving existing keratin plugs as well as preventing the formation of new ones. But compliance by users with a regimen of treatment involving repeated application of salicylic acid products is often less than ideal, because, like AHAs, salicylic acid tends to be somewhat drying and irritating and can often cause peeling, causing individuals to use the products less frequently and copiously than is necessary to obtain an optimum benefit
As noted in U.S. Pat. No. 5,505,948 to Rapport, in the prior art, peeling of the skin using acids has been done in dermatologists', aestheticians' and cosmetologists' offices, and has been accomplished in a period of minutes or hours, generally in a single visit. Such chemical peels use relatively high concentrations of such peeling agents as glycolic acid, trichloroacetic acid and phenol compounded into a suitable vehicle, with concentrations being typically from 30% up to as much as 90%, and thus are quick, harsh, and often painful. In the past, where the peeling compositions have been left on the skin under the direction of a doctor or other professional, the effect of a relatively long duration of skin contact with the peeling compositions has been wounding and irritation of the skin due to the high concentrations of the peeling agents.
Chemical peeling can be done in varying degrees of depth. A light or superficial peel is generally one which is comparatively superficial in effect, and medium or deep chemical peels are ones in which peeling agents are used to produce a moderate to severe wound to the skin. Medium or deep peels achieve a much more dramatic and visible effect, and do so quickly, in minutes or hours, but usually result in pain and inflammation of the skin. Because of the strength and attendant risks of such peels, prior art peels capable of producing significant and visible effects have been limited to use by professionals such as doctors, cosmetologists and aestheticians.
Previously, in order to be safe enough for home use, the acid concentration had to be so low that the visible, dramatic results of medium or deep peel could not be achieved by the consumer at home. It has now been surprisingly found, however, that visible, dramatic results can be obtained from a two step process safe enough for use by the consumer at home, as often as once a day.
In view of the foregoing limitations and shortcomings of the prior art compositions and methods, as well as other disadvantages not specifically mentioned above, it should be apparent that there still exists a need in the art for a product that is effective for the topical treatment of skin aging, acne etc. and for the improvement of skin appearance that is safe enough for use at home by the consumer.